Predicting schizophrenia: Calculator can predict psychosis risk

An individual’s risk for developing psychosis can be measured as accurately as a prognosis for heart disease and cancer, according to a new Yale-led study published July 1 in the American Journal of Psychiatry.

The new risk calculator assesses the risk of developing psychosis after a person experiences an early warning sign of schizophrenia — such as hearing a voice calling out the individual’s name even though he or she is aware no one is there.

“Right now, individuals and their families asking for feedback and advice after such episodes are only told about the average risk — that 15% to 25% of this group will go on to develop psychosis,” said Tyrone Cannon, professor of psychology and psychiatry at Yale and principal investigator of the study. “But with this tool, doctors can give people who have experienced early warning symptoms of schizophrenia a much more individualized assessment of risk.”

Cannon and colleagues at eight trial sites analyzed data from interviews with 596 subjects who were diagnosed with Attenuated Psychosis Syndrome — that is, people who have experienced some recent changes in perception and/or developed unusual thoughts. These individuals recognize their perceptions or beliefs are not based in reality and do not meet definition of psychosis.

In collaboration with investigators at the Cleveland Clinic, Cannon and colleagues then developed a risk calculator that analyzes known risk factors for schizophrenia. They followed up with the subjects two years later.

They found that 16% went on to develop psychosis. Those at the greatest risk of developing psychosis were individuals who were younger when their initial symptoms began and had higher levels of unusual thought content and suspiciousness, greater decline in social functioning, lower verbal learning skills, and slower speed of mental processing.

An individual’s level of risk is determined by his or her profile across these five factors, together with family history of schizophrenia and experiencing stressful or traumatic life events.

Cannon stressed that the accuracy of the calculator depends upon a trained professional’s evaluation that a patient suffers from Attenuated Psychosis Syndrome. The calculator will be particularly valuable in clinical trials testing interventions that may prevent onset of full psychosis, Cannon said.

Primary funding for the research was provided by the National Institutes of Health.